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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Avid CNC > Tramming inconsistencies at each end in both x & y directions
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  1. #1
    Join Date
    Oct 2015
    Posts
    9

    Tramming inconsistencies at each end in both x & y directions

    I'm having some difficulty tramming my machine. My sample tests are revealing a consistent high point at one end of each run. This happens when I'm tramming both horizontally and vertically. I've attached a photo of my most recent x tram test for reference. Any help you can provide would be greatly appreciated.

  2. #2
    Join Date
    Dec 2003
    Posts
    1206

    Re: Tramming inconsistencies at each end in both x & y directions

    My initial guess is movement of some kind in the mechanism as the Z axis traverses.I had a similar situation with a poorly assembled machine that did it along the table.May we see an image of the entire machine?Other helpful information would include the tool diameter,depth of cut and speed and feed.

  3. #3
    Join Date
    Oct 2015
    Posts
    9

    Re: Tramming inconsistencies at each end in both x & y directions

    Thank you for your response and thoughts. This was happening from the outset with the file provided by Avid on their website. I decided to make my own, similar file, to see if that would make a difference. Below is a screen capture of my parameters. I agree that it seems as if the Z height is changing during the milling process. I'm using a 1 inch spoilboard bit with a 90% stepover as per Avid's example. I'll try some more attempts today and see if I can spot the Z axis rising during the milling process. It's very discreet so it may be difficult to see with the naked eye.

  4. #4
    Join Date
    Dec 2003
    Posts
    1206

    Re: Tramming inconsistencies at each end in both x & y directions

    That is a very,very deep spoilboard cut.I would suggest trying about a third of that cut depth.I would be shocked if the Z axis was rising during the cut and the Gcode will probably remain unchanged.My initial suspicion would be play in the guide rails or perhaps the whole gantry is flexing sideways.If you have a dial gauge,try zeroing it against the collet nut or tool shank and apply a moderate push to the gantry to check the deflection.Do it both across the machine and along the machine and see how much movement you find.

  5. #5
    Join Date
    Oct 2015
    Posts
    9

    Re: Tramming inconsistencies at each end in both x & y directions

    That particular cut depth is a bit misleading. I've been using the same area on subsequent cuts to save wood waste. I started out with an initial cut of 1/16" (0.625) and have been increasing each cut by the same amount. As an experiment, I just now changed the tool set up parameters by stipulating the cut depth to be the same on the set up as on the individual file to see if there was some software conflicts. Unfortunately, there was no change. I also kept a very close eye on the mounting plate of the z axis during this most recent attempt to see if I could discern any vertical movement. Unfortunately, I could not see any movement, but again, that's a very discreet amount that I may not be able to detect. I don't have any dial gauges but I like your thought process. However, I suspect material movement of the soft wood rather than movement of the hardened steel of the guide rails or movement of the beefy aluminum gantry. I may just go ahead and build my spoilboard and vacuum table set up that will also have hold down clamps around the perimeter, and then try to tram once I have all that completed.

  6. #6
    Join Date
    Mar 2003
    Posts
    35538

    Re: Tramming inconsistencies at each end in both x & y directions

    My initial guess is movement of some kind in the mechanism as the Z axis traverses
    I agree. Looks like something is loose, and moving quite a bit.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  7. #7
    Join Date
    Oct 2015
    Posts
    9

    Re: Tramming inconsistencies at each end in both x & y directions

    Since my last post a few hours ago, I decided to revisit my material holding process for this tramming test. Since I just finished building my 60x60 machine and now going through the square and tramming process, I don't have a spoil board made yet that spans all the cross members and is firmly held down to the table. My test piece is a spare cutoff of MDF measuring 27" x 48". I had it held down by three Quick Grip bar clamps spanning over 4 cross members in the Y+ direction. My XYZ home area was the front left corner that was directly over one of the crossbeams. So, the starting area had a beam directly underneath it, while the rest of the cut had no solid support underneath. This leads me to believe that there is some flexing of the material as it gets pressed by the Z axis. To test this out, I started a new sample area where the cutting area was straddling a crossmember. I also added an extra clamp at this area because I noticed some very minute flexing when I press on it with my thumb. When I started the new tramming test, the first passes were looking much better. The spindle body then ran into the clamp, knocking it out of position. Guess what? Without that clamp in position, the cut in that area was much deeper.

    To test out this hypothesis, I'm going to go ahead and make my spoilboard, build my vacuum on top of that, and then install my perimeter hold downs. I'll then try another tramming test to see if this takes care of the problem. I'll let you all know how it comes out.

  8. #8
    Join Date
    Aug 2009
    Posts
    1567

    Re: Tramming inconsistencies at each end in both x & y directions


  9. #9
    Join Date
    Oct 2015
    Posts
    9

    Re: Tramming inconsistencies at each end in both x & y directions

    Thanks for the link. :wave:

  10. #10
    Join Date
    Dec 2003
    Posts
    1206

    Re: Tramming inconsistencies at each end in both x & y directions

    So now we know the plan size of the spoilboard.how about the thickness?I think there are two separate issues with this machine;first securing a suitable spoilboard and second tramming the machine.You could probably tram the machine to some extent using a piece of 1" plywood and being sure to have the spindle centred close to one of the supports for the spoilboard.You won't get far without a dial gauge and those in the link in post #8 look extremely expensive to my eyes.You won't be making chronometers on your machine and that makes a gauge that falls a little short of utterly superlative a great deal better than no gauge at all.I hope you have seen enough about the process to know that all you need is a suitable pin in the collet and a length of steel to attach the gauge to.If you can get a runout of less than 0.005" over a six inch diameter circle it wont be a disaster.One gadget you won't need is the toy that comes with two dial gauges,one is quite sufficient since you are looking for needle movement on a circular trajectory.I have been sufficiently obsessive with one machine that I did better than 0.002" on a 10 inch diameter circle-which was undone when a service technician came to perform a periodic service.Having achieved a useful initial tram you then need to find a way to hold a practical spoilboard in place so that it doesn't flex and then skim it so that it is true to the rails the machine travels on.Then verify that the initial tramming is still good enough-or re-do it.Which leads to the obvious question of how you might actually make any adjustments.

  11. #11
    Join Date
    Oct 2015
    Posts
    9

    Re: Tramming inconsistencies at each end in both x & y directions

    Update: I did a quick test using two layers of 3/4" MDF. The first layer was clamped around the perimeter to the cross members. The second, smaller piece, of MDF was screwed to the top of the first layer around its perimeter. Tramming tests were conducted in both the Y and X axis. The result was an 80% improvement. This indicates I'm on the right track. The very faint pattern similar to the photo will most likely disappear when I have the spoil board bolted down to the table and a vacuum table built on top. The vacuum should suck down any remaining MDF that is still flexing.

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